Smart-roads: Piezoelectric Transducers For Energy Harvesting
Umesh RVijaykumar M H
Sreedharkumar S R
Guided by: Dr. Venkatesh Vadde
PES Institute of Technology - ECE
Contents
• Background and motivation• Goals and deliverables• Summary of Achievements• Observations and calculations• Challenge encountered• Applications of PEH Systems• Limitations in PEH system• Conclusions
PES Institute of Technology - ECE
PES Institute of Technology - ECE
Background & Motivation
• Electricity demand far surpasses supply, and any sources of energy harvesting are very desirable
• Human actions, Kinetic energy of vehicles and ambient vibration are present every where in the environment they can be converted into useful energy
• Piezoelectric transducers are used as sensors in many applications• Piezoelectricity can be used as an energy harvesting mechanism• Motivation behind piezoelectric energy harvesting is to power mobile
devices without batteries, to control low power embedded systems etc.• Piezo-energy harvesting (PEH) from moving vehicles can power many
kinds of systems– Road warnings– Ad-billboards– Street lamps control– Traffic lights
PES Institute of Technology - ECE
Goals & deliverables
• A practical characterization of PEH-potential from commonly available piezoelectric transducer elements
• An interface circuit to condition the voltage and store the energy generated
• Quantification of energy storage potential (practically seen) in controlled & random experiments
• Demo of smart road applications powered by the harvested energy from the PEH setup
PES Institute of Technology - ECE
Summary of Achievements
• Using simple, inexpensive piezo-transducers we demonstrated energy harvesting and storage
• Designed a bridge rectifier circuit array to maximize the pulsed voltage output
• Optimized a sensor mounting mechanism for best voltage generation
• Demonstrated scaling of PEH systems from 4 discs to 16 discs all the way to 104 discs
• Discovered that vibrational mode of PEH is more effective than compressive mode
• Designed a suitable voltage regulation circuit to stabilize the pulsed voltage output of the PEH system
Study on piezoelectric elements
• Soft cushion needed under discs for producing bending stress and hence better yield
• Stacking the discs is not useful as the ceramic used in the disc is brittle. Also there are chances of shorting of the terminals.
• Using a single piezo-disc, for a normal finger pressure we could produce about 15µC of charge
• These discs when placed on vibrating materials, produce higher energy.
PES Institute of Technology - ECE
Block Diagram
PES Institute of Technology - ECE
Strain
Rectifier Filter Regulator
Battery Storage
Low power Embedded Systems
[Road warnings, Traffic lights control, Ad boards]
PiezoelectricTransducers
[Piezo element]
Waveforms at various stage
Waveforms observed
Interface Circuit
List of tasks completed
• Selection of piezoelectric transducers among available transducers• Suitable arrangement to bring out a soft cushion effect for discs• An experimental setup with 1,2,4,8 and 16 piezo-discs to show the
scaling• Quantization of charge stored on capacitor• A better interface circuit to produce constant 5V output• A larger PEH system with 104 piezo-discs to charge a Ni-MH battery• Applications in smart roads using harvested energy
PES Institute of Technology - ECE
Soft cushion for better yield
Foam Tape or rubber
Piezo buzzerStrain
• This arrangement produces soft cushion effect for better deformation of the transducer.
• Also by this way large strain could be handled without breakage of ceramic in the discs.
PES Institute of Technology - ECE
Interface Circuit
PES Institute of Technology - ECE
Scaling with number of piezo-discs
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Scale(number of piezoelectric discs)
Time (s) to charge capacitor with no load
1 120
2 65
4 35
8 20
16 5
Tabulation of time to charge 100µF cap to 10V
Scaling with number of steps
PES Institute of Technology - ECE
Tabulation of voltage at 100µFcapacitor vs. number of steps
No. of steps
Volta
ge (V
)
PES Institute of Technology - ECE
Tabulation of energy stored in 100µFcapacitor vs. number of steps
No. of steps
Ener
gy s
tore
d (m
J)Energy stored in capacitor
Capacitor voltage vs. Regulated DC Output time
PES Institute of Technology - ECE
Voltage(V) at 1000µF cap Time(s)
8 47
12 111
16 162
20 158
Voltage(V) at 100µF cap Time(s)
8 11
12 16
16 18
20 18
Time duration of 5V, 50µA Regulated DC output provided by MAX666 IC for various capacitor voltages
Larger PEH system
PES Institute of Technology - ECE
Challenges faced and solutions found
• Connecting discs in parallel results in deformation in other discs.Connecting discs in series adds up voltage but, when the strain is not
synchronized subtraction happens.Solution: Connecting rectifier for each piezo-disc.Now series combination does not work because when one of the disc
is not deformed it results in open circuit.Parallel connection works – Capacitor is charged when any of the disc
is deformed irrespective of synchronization.
• Voltage drop in rectifier diodes is considerable i.e. 0.6+0.6=1.2VSolution: Using diode 1N5817/18/19 results in voltage drop of just
0.15+0.15=0.3V
PES Institute of Technology - ECE
Challenges faced and solutions found
PES Institute of Technology - ECE
Challenges faced and solutions found
• Use of linear regulators like IC7805 leads to more power dissipationSolution: Using MAX666 IC , a micro power voltage regulator which is more
efficient and can produce a constant stable output for a particular duration
• Vibrations produce more energy, but to convert the strain of vehicles into vibrations at discs a complex setup is required
PES Institute of Technology - ECE
Applications
• Road lines and road signs illumination at night efficiently• Efficient road lamp switching to save power (Only when a
vehicle approaches light glows)• Approximate measure of weight of the vehicles• Measurement of speed of vehicles
PES Institute of Technology - ECE
Limitations of current PEH system
• Piezoelectric transducers are high impedance (low current) sources of power
• PEH system to provide continuous output power requires higher density of vehicles which cannot be guaranteed
• The ceramic piezoelectric material is brittle• Rather than strain, vibrations produce more energy. To
achieve vibrations we need a complex setup
PES Institute of Technology - ECE
Conclusions
• Developed a modular, scalable PEH mat that can be deployed on roads, corridors, elevators as smart solution
• Piezoelectric energy harvested is best suitable for low power, embedded, programmable applications
• PEH system works in any weather condition compared to solar energy which depends on weather
• Many smart road applications can be realized using piezoelectric energy harvesting:– Intelligent traffic control– Intelligent street lighting– Cautionary flash-signs
PES Institute of Technology - ECE
References
• http://www.piezocryst.com/piezoelectric_sensors.php• www.innowattech.co.il• http://en.wikipedia.org/wiki/
Energy_harvesting#Piezoelectric_energy_harvesting• www.designboom.com/technology/intelligent-interactive-highway-by-
studio-roosegaarde-heijmans/• http://www.americanpiezo.com/knowledge-center/piezo-theory.html• http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6145389• www.fusionteq.com/html/battery_101_-_the_basics.html
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Thank You